Internal combustion engines (ICE) are often called upon to generate considerable levels of power for prolonged periods of time on a dependable basis. Many such ICE assemblies employ a supercharging device, such as an exhaust gas turbine driven turbocharger, to compress the airflow before it enters the intake manifold of the engine in order to increase power and efficiency.
Specifically, a turbocharger is a centrifugal gas compressor that forces more air and, thus, more oxygen into the combustion chambers of the ICE than is otherwise achievable with ambient atmospheric pressure. The additional mass of oxygen-containing air that is forced into the ICE improves the engine's volumetric efficiency, allowing it to burn more fuel in a given cycle, and thereby produce more power. Frequently, such turbochargers are driven by the engine's exhaust gases.
A typical exhaust gas driven turbocharger includes a central shaft that is supported by one or more bearings and that transmits rotational motion between a turbine wheel and an air compressor wheel. Both the turbine and compressor wheels are fixed to the shaft, which in combination with various bearing components constitute the turbocharger's rotating assembly. Turbochargers frequently employ waste-gate valves to limit operational speeds of the rotating assembly in order to maintain turbocharger boost within prescribed limits and prevent rotating assembly over speed.